This invention pertains to the field of animal litters, especially Cat Litter, a granular product used to receive and absorb animal wastes for subsequent disposal. Such materials have many existing problems. The earliest such materials were drawn from the field of spill adsorbing materials, such as had been widely used to adsorb oil and liquid spills. While such materials resembled sand or dirt, and thus were acceptable to the animal, representing an instinctive place to deposit and bury wastes (cats will not place wastes where they cannot be buried.), they only adsorbed and held urine. This decomposed, and became the source of odor, requiring frequent replacement and disposal of the litter.
Subsequent developments have concentrated on providing a method for disposing of both solid wastes and liquid wastes. This led to the development of clumping litters, in the form of finely ground granules of certain clays, sometimes augmented by binders or additives. These granules clump in the presence of liquid wastes, which then can be scooped up and removed with the solid wastes.
However these fine granular clays present additional problems. The most irritating is that these materials produce continual dusts, both during manufacture and shipment, and as the litter is disturbed during use. Consumer surveys have indicated that the presence of dust is the most common complaint about cat litter, because of the cleanliness problem animal litter dust presents in a household environment. Further, the dust clings to the fur and paws of the cat, and is tracked throughout the home, or is ultimately ingested by the animal during grooming; both results are equally undesirable.
The composition and manufacture of these prior art litters are shown, for example, in the following:
U.S. Pat. No. 4,704,989 to Rosenfeld discloses a process for producing cat box litter which comprises taking a fine clay dust, disclosed as either predominantly kaolin or bentonite, wetting it with a mixture including an adhesive-type soluble lignin (obtained as a by-product from paper treatment) and then extruding the wet mixture through a pellet or pin type agglomerator. The resulting pellets are screened and then dried to be not more than 29% by weight water and preferably 5% by weight water to create an absorbing clay litter.
U.S. Pat. No. 4,459,368 to Jaffee and others discloses the use of a combination of Fuller's earth, preferably in the form of calcium bentonite, mixed with calcium sulfite dihydrate. In this patent, both the clay and the calcium sulfate dihydrate (synthetic granules) are individually screened to a desirable particle size, an example being 6 mesh, and then are mixed as particles to form a mixture which is then the claimed cat litter.
EUROPEAN PATENT 424001A1 to Hughes discloses an animal waste absorbent formed of water-expandable bentonite clay originally provided in discreet particles of between 50 and 3350 microns. This material is claimed to form clumps, after one to twenty-four hours exposure to liquid animal waste, which can be easily removed. The clumps are not physically bound and will dissolve in water but are physically stable enough to be removed from the remaining powder.
U.S. Pat. No. 5,129,365 to Hughes is the U.S. Patent corresponding to the European patent discussed above.
U.S. Pat. No. 5,188,064 to House claims a clumping cat litter comprising a mixture of a clumping clay such as shown in the Hughes' patent, together with cellulose and a material such as a non-swelling clay to adjust the density of the resulting cat litter. The mixture is provided as a mixed powder of the various ingredients, sized typically within the range of two hundred fifty microns to 2000 microns for both the clays and the cellulose.
U.S. Pat. No. 5,101,771 to Goss discloses a clumping animal litter made of free-flowing clay particles coated with an organic biodegradable clumping agent suspended in an oil-like vehicle and distributed over the surface of the clay particles. This patent differs from the prior patents in that the principle clay component is chosen those clays considered not suitable for use in the House and Hughes patents. The clay particles are themselves screened particles stated to be between a 4 and 60 mesh, preferably 20 to 60 mesh. The particles are then coated with the clumping agent, preferably a cellulosic ether such as methyl cellulose, carboxymethyl cellulose or hydroxypropylmethylcellulose. The clumping agent and an oil mixture are sprayed upon the clay particles.
U.S. Pat. No. 4,591,581 to Crampton and others discloses a process for making absorbent clay mineral particles: mixing the dried particles with up to 5% by weight of a water-dispersed colloid; compacting the material in a press; and then breaking the compacted material into masses of smaller particles. The material is disclosed as useful for a litter. The suggested colloid is a vegetable gum such as guar gum or derivatives. These colloids are described as particularly enhancing the clumping properties of the litter. The process disclosed mixes the clay fines with a water-dispersed additive having such colloidal properties, disclosed types including a silicate, a pyrophosphate, or a polysaccharide. The amount of the colloidal agent is limited to 5% or less by weight to the clay. The clay mixture is compacted in a roll mill and then broken into smaller particles to form a particulate litter.
U.S. Pat. No. 5,193,489 to Hardin discloses that the clumping ability of a poorly clumping clay may be enhanced for use as a litter by mixing the clay with a water-soluble or dispersed gum such as a guar gum or derivatives. This patent includes the disclosure that a polysaccharide may be used as one of the agglomerating gums.